


The Ultimate Device for Understanding

by RawSunset (Mislagnissa)



Category: Ben 10 Series
Genre: Alien Sex, Alien/Human Relationships, Alternate Universe - Fusion, Alternate Universe - Gender Changes, Ben 10 Classic, Ben 10 Reboot (2016), Blow Jobs, Crossdressing, F/M, Facials, Female Ben Tennyson, Frottage, Genderbending, M/M, Masturbation in Shower, Other Additional Tags to Be Added, Plot What Plot/Porn Without Plot, Stripping, Tentacles, two Dicks
Language: English
Status: In-Progress
Published: 2020-04-21
Updated: 2020-11-25
Packaged: 2021-03-01 05:07:18
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,246
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23399686
Author URL: https://archiveofourown.org/users/Mislagnissa/pseuds/RawSunset
Summary: Azmuth created the Omnitrix to be "the ultimate device for understanding." Since it was a work in progress, it was prone to glitches (and the Antitrix was even glitchier). This included two recurring bugs that were especially relevant to Ben.Firstly, the watch could not distinguish Ben's DNA from her grandfather's because humans had <1% variation. So all of her alien forms were male, where applicable.Secondly, sometimes the watch got stuck in an alien form for hours or even days at a time. Whenever that happened, Ben and Kevin sometimes used the opportunity to appreciate their new forms.And how.
Relationships: Kevin Levin/Ben Tennyson, Other Relationship Tags to Be Added, Quad Smack/Wildvine (Ben 10 Series), Ripjaws (Ben 10 Series)/Kevin Levin
Kudos: 14





	1. Kevin and Ripjaws at the pond

**Author's Note:**

> For reference on Kevin's different wardrobes and hair styles, [see this sketch by Sunghwan Steven Choi.](https://i.imgur.com/MaPEkKv.jpg)

**Summary for the Chapter:**

> Ben gets stuck as Ripjaws, he goes swimming in her grandpa’s secret fishing hole with Kevin, (re)discovers the watch's glitchy wardrobe function, both get horny, and Kevin goes down on our fishy hero.

**Notes for the Chapter:**

> I apologize in advance. This is my first time ever writing erotica.
> 
> The bad puns were intentional, though.

Ripjaws breached the surface of the water and took a big gulp of fresh air. He grinned broadly at the feeling of cool water washing over his muscular body and gills, at the rush of nature’s power washing over his body. He imagined that this must have been a bit like what being a dolphin felt like.

He waved at the shore of the pond. Kevin stood there, still in the middle of stripping down. Next to him were two towels laid on the sand. Next to one sat a bulky respirator, an addition by one of the occasional Omnitrix updates that Azmuth deigned to share with Ben. Ripjaws did not need to hydrate while swimming, so he took off the respirator for the feeling of clean air and freshwater against his scales. Next to the other towel was a camo print backpack, unzipped. Its former contents, a pair of red swimming trunks, lay on the towel.

“Come on in Kev! The water’s fine,” called the piscine alien, waving. Despite his lack of lips, the alien’s syrinx could mimic human speech fairly well.

“Give me a minute, Benji,” Kevin called back.

Ripjaws chuckled. “Too chicken for skinny dipping?” he asked himself. The fishing hole was isolated. Nobody would discover him if he did.

While Kevin was distracted with stripping, Ripjaws quietly swam over. The black plates of his tail split along the sides, revealing a pair of legs. He stepped out onto shore. His tail plates retracted, transforming into a loincloth. The ravenette had already stripped off his shirt and shoes and was in the middle of taking off his denim jeans. The alien took a few more steps until he was a couple of arm’s lengths away from the boy. The latter faced away, so he did not notice the approach.

Kevin had grown up so much since they had first met in elementary school. His messy hair was drawn back in a ponytail, giving his forehead a slight widow's peak and pronouncing his sideburns. By far the biggest change to the boy’s face, Ripjaws thought, was his triangular goatee.

His large silvery-green eyes glanced up and down, admiring the human’s athletic physique. Kevin tugged down his denims and his trademark black briefs. This gave Ripjaws an eyeful of his firm rear, toned like a gymnast's from his adventurous crime-fighting lifestyle. Combined with his broad powerful shoulders, the ravenette would attract the gaze of almost every girl as he walked through the halls of Madisson High (and some boys, too).

Even ensconced within the virtual environment of the Omnitrix and barely aware of her own body, Benjamin Kirsty Tennyson would have been lying through her teeth if she said she was not attracted to those rippling cheeks. Although Ripjaws was an avatar cloned from the Piscciss Volann genome, their nervous systems were still synchronized (with aid of her own genome spliced into his, required for neural compatibility… and glitched out due to being programmed to respond to grandpa Max’s genome, but unable to distinguish grandfather from granddaughter because humans had less than one percent variation in their genomes). She felt what he felt and vice versa. Right now, Ben could feel something stiffening beneath Ripjaw’s loincloth.

She tried to stifle her gasp, but it was too late. The alien took a deep breath, then spat a torrent of water at the boy.

Kevin cried out in surprise, tripped over his pants, and fell over onto the sand. “Hey, cut it out Benji! Would it kill ya to wait ‘til I put my trunks on?” he said, shivering and sputtering. He grunted as he pulled his remaining clothes off and stood back up. He held up the dripping cloth in one hand. “Now my pants are soaked, damnit!”

Ripjaws rubbed the back of his head sheepishly, his scales darkening as the blood rushed to his face. “Sorry, Kev, I got excited. I’ll make it up to you.”

Kevin sighed. “It’s fine, I can just hang up to dry on a tree.”

Ripjaws’ hands moved to fumble with the Omnitrix dial at his waist. A recurring bug was that the dial had the tendency to randomly change position every so often: in Ripjaws case it tended to switch between his left shoulder, middle of his chest, and his navel (or at least where his navel would have been, since Ripjaws was not a placental mammal).

There was a flash of green light. The harshness caused Kevin to reflexively blink a couple of times. When he could see again, Ripjaws’ black-and-yellow loincloth was replaced by a pair of green pants.

“Wow,” said Kevin. “There’s a wardrobe function?”

Ripjaws shrugged and replied, “There is now.”

He made eye contact with Kevin and noticed the ravenette’s dark eyes slowly widen. His silvery green eyes followed the other boy’s gaze to the crotch of his new green pants. There was a noticeable bulge in the front of the green alien fabric. The bulge slowly grew bigger by the second, pitching a large tent in the new pants. The alien fabric stretched and clung tightly yet comfortably to the piscine alien’s body in a way that spandex could only dream of, leaving little to the imagination. Ripjaws could feel the scales of his face getting even hotter.

Water dripped down the alien’s ripped torso and down the tent. Rivulets flowed across the fabric without being absorbed. The alien could have walked out of a showergel commercial or an ancient book recounting the very sexy misadventures of a neptunian Priapus.

Kevin audibly swallowed and averted his gaze from the stiffening erection. He raised one hand to scratch compulsively at the nape of his neck. “Some kind of smart nanomesh. Form-fitting, comfortable, waterproof. Galvan tech, am I right?” he rambled.

Ripjaws’ eyes darted to the other boy’s crotch. A line of black hair ran down from Kevin’s navel into a thick patch of curly hair. The boy’s cock was already flush and pointing diagonal to the ground, the skin darkening and a set of thick veins blatantly visible on the shaft pulsing with hot blood.

As Ripjaws watched, Kevin’s cock engorged with his hot red American blood. The erected shaft rose stiffer and stiffer, twitching this way and that as if with a mind of its own. The foreskin pulled back as the cock grew too long to contain, revealing a dark head that quivered with desire.

The alien could not avert his eyes. Now risen to its full length of eleven American inches, the twitching pulsing shaft stood almost parallel to the ground. Below hung the boy’s two succulent balls, one noticeably lower than the other, the outline of his sack barely obscured by his pubes. His package could not have been smaller than a pair of eggs from the grocery store.

The two made eye contact again.

Ripjaws gulped loudly. “L-Looks like we b-both have a p-problem,” he said.

What felt like an eternity passed, but could not have been more than a few seconds.

Kevin’s cheeks and ears were bright red. He glanced around and stuttered a couple of nonsense syllables before asking, “You want me to take care of that?”

Ripjaws made a needy whimper and nodded.

Kevin dropped the soaked denims he forgot he held. He stepped toward Ripjaws. The two stood facing each other, their twitching cocks saluting. Kevin leaned forward and placed both hands on the larger alien’s sides. He raised one hand to Ripjaw’s pecs, then the other, feeling the skin under his palms. It was far smoother than any terrestrial fish, more like a dolphin or an alligator. The ravenette experimentally flicked his thumbs across the alien’s dark green nipples, already perked up in the summer air. The taller alien quivered at the touch.

“Lie on the towel,” ordered the ravenette, “it’ll be easier that way.”

Ripjaws obligingly stepped away and walked onto the towel. He sat down and rested his back against the towel, the fabric warmed by the hot sand.

The ravenette knelt before the piscine alien, who spread his legs apart in response. Kevin scooted forward until his face was so close that his nose nearly touched the tip of the tent in the alien’s pants. He licked his lips and raised a hand to the tent, cupping the bulge through the fabric. Ripjaws bit back a moan at the sensation. The bulge jerked, nearly slapping Kevin in the face.

The boy chuckled. He raised both hands to the hem of Ripjaws’ pants, one on either side of the alien’s hips. With deliberately exaggerated slowness, he pulled down the pants. Every second, less than an inch of the hem moved lower. Ripjaws whimpered again, the fabric rubbing like silk against his hardness. A shit-eating grin split Kevin’s face as he watched inch after inch of green alien dick reveal itself to his leering eyes.

It was too much for Ripjaws. His quickering hips bucked, pulling the seat of his pants the rest of the way. The hem came to a stop around his thighs, just below his crotch.

Kevin barely reacted as the alien’s length, freed from its confinement, smacked him across the chin. He involuntarily closed his eyes as his chin lifted upward. A moment later he looked forward again and came face to face with a sight that caused him to gape like a fish.

A ten inch alien dick twitched in front of his eyes, bright green from base to tapering tip. It was not as long as Kevin’s endowment, but it was definitely thicker. Right next to it, another identical shaft twitched and wept like a leaky faucet. There were no pubes and no sack beneath. Just a weeping slit in Ripjaw’s crotch, the two cocks jutting out of it like a pair of twin torpedos.

“Oh my God,” said Kevin. “Talk about putting the ten in Tennyson.”

(It did indeed run in Ben’s family, even if she only learned that detail after stealing her grandma Verdona’s secret lewd diary. Not that she would normally consider her alien forms family, no matter their genetic relation.)

He pulled down the pants the rest of the way, the alien’s legs helpfully limp in the boy’s grasp, and threw the clothing onto the other towel. (He would need those pants later.) He eagerly grabbed Ripjaws’ left cock in one hand and leaned forward, lips apart. His other hand moved down to his own erection, pumping his American wiener like one of the pistons in the engine of his beloved car. His tongue darted out and licked the slippery tip. He moaned at the unexpectedly agreeable taste. Kevin had expected it to taste revolting, like the way that uncooked fish smelled. He could not find the words to describe the taste, but it was closer to the way that cooked fish smelled. He slurped the first couple inches into his mouth, the tip of his tongue dipping into the piss-slit.

“Kevin, wait!” cried Ripjaws, but it was too late. His heads exploded, releasing their payloads like the torpedos they resembled.

Hot cum erupted into Kevin’s mouth, while the other cock sprayed cum onto his cheek. There was too much to fit into his mouth and he was not prepared to swallow any of it, so the excess sprayed from the tight space between his lips and the cock. He pulled back in shock, releasing the erupting volcano of a dick. Both cocks sprayed their white-hot neptunian seed across his face and shoulders.

Kevin moaned as his own cock erupted, spraying his essence across the towel and Ripjaws legs. The secondary lights in the Antitrix on his wrist blinked wildly, like it was having a seizure.

Floating insensate inside of the Omnitrix’s virtual void, Ben threw her head back and screamed in ecstasy as the feeling of Ripjaws’ orgasm rippled down her spine. One hand unconsciously flew to her crotch and squeezed. Wetness soaked through her green boxers. For just a moment she imagined Kevin E. Levin’s eleven inch American wiener buried itself inside her, spraying his thick boiling osmosian mutant seed deep inside her womb.

Kevin and Ripjaws both collapsed against the towel, drenched with their own essence (mostly the latter’s), breathing heavily. Kevin wiped jizz off his chin and said, “I don’t think I can go swimming right now.”

As if on cue, the Omnitrix made its characteristic beeps. Once again Kevin was momentarily blinded by green light. When he looked back at Ripjaws, all he saw was Ben lying on the towel. She was fully clothed and, to all outside appearances, conveniently completely clean.

Kevin glanced over at the other towel, and gave a sigh of relief when he saw the green nanofiber pants were still there. Omnitrix glitches were not all bad, it seemed.

Ben glanced down at her pristine appearance, then at her boyfriend drenched in musky alien jizz. She wrinkled her nose.

“You have to go sometime, Kev. You stink like fish,” she replied.

The couple stared at each other for a moment, then both burst out laughing.


	2. Wildvine and Quad Smack in Kevin's garage

**Summary for the Chapter:**

> Ben and Kevin get temporarily stuck as Wildvine and Quad Smack after a mission. The two crash in Kevin's garage while they wait for their watches to time out correctly. Quad gives Wildvine a striptease and a show in his portable shower stall. Wildivine appreciates Quad's doubled anatomy and shows off some new tricks he learned with his vines.

**Notes for the Chapter:**

> Wildvine’s design here is that of his reboot incarnation. Tiny yellow flower collar, only two legs.
> 
> He’s also wearing a pair of green shorts. You’ll see why.

With Kevin’s car sitting quietly in the driveway, Wildvine and Quad Smack walked up the flat black pavement to Kevin’s house. The violet alien stopped in front of the garage, the door of which was closed. He knelt down, grabbed the handle, and casually lifted the garage door.

The garage was currently filled with assorted household objects, like a fairly worn couch that immediately caught Wildvine’s eye, plus whatever alien tech and other knick-knacks Kevin brought back home from their adventures.

“Wow, this place is a mess,” said Wildvine.

“Whatever. I was planning on cleaning it out later anyway,” replied Quad Smack

Quad Smack casually strode inside and Wildvine followed his lead. The floral alien reached up his vines and closed the door behind them, then walked over to the couch and sat down, crossing his legs and slouching. His green shorts creased, emphasizing the bulge of his package.

In one corner of the garage was an indoor portable shower. It was a rectangular cuboid with an aluminum frame holding four transparent glass walls. It was plenty large enough for two or three people, so it was just the right size for Quad Smack or any similarly sized alien form.

The violet tetramand’s four red eyes briefly brushed over the shower. He lifted one arm and sniffed his own pit. He immediately turned his head away, gagging.

“Man! I stink!” he said.

“Don’t be so hard on yourself, Kev. It was a pretty tough fight,” said Wildvine.

“No, Benji. I mean I literally stink. The watch’s been stuck for so long that I’ve gotten alien BO.”

“Oh.” The florauna briefly lifted one of his own arms and sniffed himself. “I don’t smell anything,” he said.

“You don’t even have a nose!”

The green alien’s single eye widened as he gasped in mock shock. “I can’t believe what I’m hearing!” he replied in mock offense.

The violet alien smirked back. “How can you hear it? You don’t have ears either!”

Wildvine burst out laughing, followed a moment later by Quad Smack.

“But seriously, Benji,” Quad said after they finished. “You mind if I take a shower?”

The tetramand did not stop to wait for an answer, as he immediately pulled off his gloves two at a time. Then he reached up and pulled off his shoulder pads at once, followed by bending down and pulling off his boots one by one.

Wildvine shrugged. “Really? Like right now? Eh, okay, sure?”

Quad grabbed the hem of his red-and-black shirt and lifted it up and over his head, giving Wildvine an eyeful of the tetramand’s rippling back muscles, toned eight pack abs, and two pairs of bulging pecs covered in dark curly hairs. Black stripes criss-crossed his torso, giving him a tigerish cast. All four of his thick succulent nipples were so dark that the skin almost appeared black, and quickly perked up as the cool air of the garage hit them. Quad sighed as he felt the prickling sensation of goosebumps rising across his arms and chest. He experimentally flexed his arms and turned around a few times.

“Damn, you’re so hot right now,” said Wildvine from his excellent vantage point on the couch. “I wish I had four hands.” A pair of vines immediately sprouted from the buds on his back, ending in a pair of flexing hands to give him a total of four. He grinned. “Oh wait, I do.”

Quad smirked at the green boy’s enthusiasm for the improv strip show. “Hold that thought Benji,” he said. “If you liked that, then you’re gonna love what’s up next.”

The violet hulk turned his back to his teammate, grabbed the waistband of his pants, and pulled them down in one go. 

“O-M-G,” said Wildvine.

Quad was now wearing nothing but his Antritrix and a red jockstrap, giving his floral boyfriend another eyeful of his toned thighs, glutes, the black tiger stripes emphasizing his hot alien ass. The violet boy sinuously gyrated his hips a few times before turning around to reveal the red cup of his jock, bulging like a Christmas stocking with his alien package hidden inside.

Quad glanced back at his boyfriend and smirked at the tent rising in the latter’s shorts. “Looks like somebody’s up and ready for me,” he said. He walked right up to Wildvine and sat down in his boyfriend’s lap, pressing their cloth-covered hardons together.

A dopey grin split Wildvine’s face. He raised all four hands and ran them across his violet boyfriend’s hairy pecs, feeling the warm rippling muscles beneath his touch rising and falling with the hunky alien’s every breath. He leaned forward and stuck out his tongue, licking upward between the cleavage of the lower pair of pecs. He tasted salt and something unpleasantly pungent.

He reluctantly pulled back and lowered his hands back to the couch. “Yeah, you definitely need a shower, Kev,” he said.

“If you say so,” Quad replied. He shifted and moved to sit on the couch next to his green boyfriend. He raised his legs slightly off the floor, grabbed the waistband of his jock, pulled it down his legs and off his feet in one smooth motion, then tossed the cloth to the floor. He stood up in front of the couch, giving a full view of his manhood.

What a manhood it was. His crotch was crowned with a thick bush of black curly hair that trailed all the way up to his navel. Two eleven-inch erections rose from the violet alien’s crotch, standing almost parallel with the ground. Below them hung a sack heavy with four baseball-sized orbs, with thick veins running along the skin and aching with need.

Wildvine’s previous dopey grin returned and widened even further, if that was possible. “So that’s why the baseball team calls you ‘Two Bats’,” he said dumbly. “One for the bat in your hands, and one for the bat in your pants.”

Quad chuckled. “Wouldn’t that be ‘Three Bats’?” he asked.

The florauna’s single eye suddenly narrowed in confusion. “Do I still get to play?”

The tetramand cupped his crotch with one hand and playfully fingered his cocks. “Don’t worry, I’ll keep the bats hard for you, Benji.” He leaned forward and kissed his boyfriend’s forehead, then stood straight and walked over to shower.

  
Quad Smack opened the shower door. He adjusted the single knob handle to a comfortable temperature, causing the showerhead to spray cool water. He wanted a moment for the water to heat up. Satisfied at the temperature, he stepped inside and closed the door behind himself.

The transparent walls of the shower gave his boyfriend full view of the violet boy’s body as water cascaded across it. Quad leisurely rubbed the water across his pecs and arms. In the corner of the shower was a shelf with bottles of soap and a long-handled brush. He picked up and opened a bottle of body wash and applied the soap to himself. With deliberate slowness he rubbed the suds across his body.

With one hand he fondled and played with his cocks, already weeping pre. He pulled back the foreskins to reveal bulging heads with skin so dark it was almost pitch black, supplied with blood by thick bulging veins running along their shafts. Another hand pinched and thumbed a nipple, already stiffened in the cool air, more to give his boyfriend a show than for his own pleasure. Then he let the water rinse himself clean, washing off the grime of the day from his pubes and pits and everywhere else.

At some point Wildvine had started touching himself through the fabric of his shorts. Now he opened his fly and pulled out his vermillion stamen, the ten-inch shaft and egg-sized balls standing out starkly against the lime green of his shorts. With one hand he slowly pulled back the foreskin, baring a brilliant yellow anther that dripped like a leaky faucet. With the other he cupped and fondled his balls, which subconsciously ached with the desire to pollinate. (Ben had no idea how much of Wildvine’s manhood owed to the natural flower of a florauna or to her own human Tennyson genes. Not that she was not about to complain or anything of the sort.)

By this time the shower glass was starting to fog up. Quad shut the water off. Then he opened the door, walked out, and grabbed a clean towel from a nearby rack. He dried himself off and then walked over to the couch again, still holding the towel in one hand. Completely naked, he sat back next to his boyfriend with one pair of arms behind his head. His twin cocks pointed almost straight up in the air, like Ancient Egyptian obelisks in miniature.

“Oh my God,” said Wildvine. He stared at Quad’s erections, a drop of spit absently collecting in the corner of his mouth.

“What a big stamen you have.”

“All the better to pollinate you with.”

“So what do you want to do first?”

“I wanna touch them.”

“Go ahead, I need a hand.” A shit-eating grin split Quad’s face.

Wildvine smirked back. “I have a better idea. Want to see something cool?”

“Sure.”

Wildvine extruded a pair of vines, these ending in yellow flowers. The vines slithered toward Quad’s lap and the flowers brushed back and forth against his balls. Some kind of fluid dripped from the blossoms.

Quad gasped.

“What’s wrong?” said Wildvine. “You don’t like it?”

“No, I do, Benji!” said Quad. He extended a hand and reassuringly squeezed Wildvine’s shoulder. “They just feel like tongues. That’s new.”

“Exactly. Now watch this.”

The two flowers rose and lapped against Quad’s cocks, one for each. Drops of pre dripped down the violent obelisks, which the petals licked up greedily. Quad tilted his head back, eyes closed, tongue lolling out the corner of his mouth. His breathing quickened and he released a moan. While the two flowers were busy, Wildvine raised a hand to Quad’s chest and fondled an erect nipple. 

“How’d you learn to do this?” asked Quad.

“I practice when you’re not around,” replied Wildvine.

The two flowers moved upward and, in perfect synchrony, engulfed the leaking heads of Quad’s purple cocks. The flowers bobbed up and down like a pair of fleshlights, their eager maws drooling nectar. The veins in Quad’s cocks bulged, pulsing with desire.

“Oh fuck yeah,” said Quad.

“If you like that, then you’re gonna love this.”

Wildvine carefully adjusted his position and crawled into Quad’s lap. He placed his erect dripping stamen between the tetramand’s cocks, his green balls lightly slapping against the violet balls of his lover. Quad’s eleven-inch torpedoes were definitely longer than Wildvine’s ten-inch stamen, but the latter was noticeably thicker in girth. The florauna thrust his hips forward, rubbing his erection between the tetramand’s twin shafts, in rhythm with the bobbing of his flowers.

The violet alien grabbed either side of Wildvine’s little green shorts with one pair of hands, and casually tore the article off the florauna’s body. With his other pair of hands he grabbed Wildvine’s toned green bubble butt, one hand gently squeezing each cheek.

“A dickjob and a double blowjob?” asked Quad. “Aren’t you the kinky one, Benji? And resourceful too.”

“Well, I have saved the Earth at least three dozen times.”

“Hey, I was—”

Quad’s rebuttal muffled as Wildvine leaned forward and captured the other’s lips with his own, their tongues entering each other’s mouths to savor the taste of the other. The florauna’s current two pairs of hands roamed the tetramand’s ample pecs, caressing nipples and occasionally twirling chest hairs.

Their three cocks were dripping like active volcanoes, ready to explode at any second and rain everywhere.

Quad broke the kiss, panting. “B-Benji, I’m gonna cum.”

“Me too, Kev,” replied Wildvine.

The two moaned as one. Wildvine erupted first, his cock spraying thick spurts of his pollen all over Quad’s abs and pecs. Before he had even finished his second spurt, Quad’s twin torpedoes shot ropes of his hot cum like miniature fire hoses right into the former’s hungry pistils.

After what felt like an eternity, but was only a few moments, the green boy collapsed against his violet boyfriend. His vines went limp, his dripping pistils pulling away from Quad’s softening cocks and falling to his sides. The two breathed heavily, basking in the afterglow.

“I’m gonna need another shower.”

“Me too.”


End file.
